如何使用角度材料步进器和角度6来激活selectedIndex步的前所有步骤

<mat-horizontal-stepper>
  <mat-step label="Step 1">
    <!-- Step 1 content -->
  </mat-step>
  <mat-step label="Step 2">
    <!-- Step 2 content -->
  </mat-step>
  <mat-step label="Step 3">
    <!-- Step 3 content -->
  </mat-step>
</mat-horizontal-stepper>

import { Component, ViewChild } from '@angular/core';
import { MatStepper } from '@angular/material/stepper';

@Component({
  selector: 'app-my-component',
  templateUrl: './my-component.component.html',
  styleUrls: ['./my-component.component.css']
})
export class MyComponent {
  @ViewChild(MatStepper) stepper: MatStepper;

  activateAllPreviousSteps() {
    const selectedIndex = this.stepper.selectedIndex;
    for (let i = 0; i < selectedIndex; i++) {
      this.stepper.selected.completed = true;
      this.stepper.next();
    }
  }
}

<button (click)="activateAllPreviousSteps()">Activate All Previous Steps</button>